204 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



segmentation 



'O 



1 



o 



C/3 

 0> 



bJO 



anterior end 



o 

 bfl 





bJO 



> > 

 ' 'S 



WO b/J 



iT o 



'e .2 



ft g 



s 



1 



^-> 

 rt 



.a 



o 



15 I 



a I 



n3 



G o 



phophore or 





